Orlando, Fla. (AP) - Republican Sen. Mel Martinez of Florida said Friday he will resign from the Senate as soon as a replacement can be appointed, leaving the seat more than a year before his term ends.

Martinez, the only Hispanic Republican in the Senate, revealed his plans in a statement to supporters and was expected to publicly announce the decision Friday afternoon in Florida.

The first-term senator already had announced in December that he would not seek re-election in 2010, but he had fended off rumors that he would give up the seat early.

His decision puts Republican Gov. Charlie Crist - who is running to replace Martinez - in charge of filling the seat in the interim. Crist said Friday as he boarded a plane to Tampa that he will not appoint himself, but he declined to discuss the issue further.

In his letter to friends and supporters, obtained by The Associated Press, Martinez says he's stepping down early for personal reasons.

"My priorities have always been my faith, my family and my country, and at this stage in my life, and after nearly 12 years of public service in Florida and Washington, it's time I return to Florida and my family," Martinez wrote.

The note says his resignation will be "effective on a successor taking office to fill out the remainder of my term."

Officials predicted that Crist, who faces a Republican primary challenge and a large field of Democratic contenders, would select a "placeholder" for the temporary assignment.

Martinez, 62, was elected in 2004 after serving as the U.S. secretary for housing and urban development under President George W. Bush. He served as general chairman of the Republican National Committee for 10 months, resigning in October 2007.

He was born in Cuba. At the age of 15, he fled to America as part of a Catholic humanitarian effort called Operation Pedro Pan. Catholic charitable groups provided Martinez, who was alone and spoke virtually no English, a temporary home at two youth facilities. He then lived with two foster families, with whom he remains close. He was reunited with his family in Orlando in 1966.

Martinez has denied that he was forgoing a second term because of concerns about difficult re-election prospects in a state won by President Barack Obama. But he has struggled to boost public support because of his close ties to former President George W. Bush and his efforts pushing an immigration bill that was unpopular with many Republicans.

His resignation leaves just one Hispanic in the Senate, Democrat Robert Menendez of New Jersey.